Rolling bearings are mounted to moving parts of transportation machines, industrial machines, or various other machines. Some of such machines include an operation mechanism which needs to be lubricated by oil, such as the portions of gears meshing with each other, or the portions of components in sliding contact with each other, and are configured such that the operation mechanism and the rolling bearings are lubricated by common oil.
For example, devices such as oil pumps include, in their interiors, a rolling bearing and an operation mechanism, and are capable of sending lubricating oil contained in the devices toward an outside operation mechanism located outside of the devices.
Foreign matter such as wear dust (iron dust, etc.) may occur in the bearing space of the rolling bearing of such a device. If foreign matter enters the operation mechanisms located midway of the circulation path through which lubricating oil circulates, such entry may reduce the durability of the device, damage the device, or cause the device to malfunction or fail to operate in an accurate manner.
In order to overcome such a problem, for example, Japanese Unexamined Patent Application Publication No. H07-280180 (hereinafter JP H07-280180) discloses an iron dust contamination detecting method for detecting the contamination of lubricating oil by iron dust such that a waning is sent when, if foreign matter such as iron dust enters lubricating oil flowing in a circulation path, the foreign matter is attracted to magnets mounted to a sensor, and accumulates on the magnets such that a metal casing and the magnets are electrically connected to each other through the accumulated foreign matter.
As described above, it is not preferable that foreign matter such as wear dust (iron dust, etc.) occurring in the rolling bearing enters the operation mechanism located midway of the circulation path through which lubricating oil circulates. In particular, if the rolling bearing is used in an oil pump, large separated pieces occurring in the rolling bearing may damage components of the operation mechanism inside of the oil pump, and/or components of the operation mechanism located midway of the circulation path through which lubricating oil sent out by the oil pump circulates, or cause these component to malfunction or fail to operate in an accurate manner. Therefore, it is necessary to prevent foreign matter occurring in the rolling bearing from flowing out of the rolling bearing, and to detect the occurrence of such foreign matter.
In JP H07-280180, the magnets of the sensor face the interior of the circulation path through which lubricating oil circulates, but most foreign objects contained in lubricating oil flowing in the circulation path may pass by the magnets without being attracted to the magnets. Also, in JP H07-280180, the magnets attract/catch only a small amount of foreign matter necessary for detecting how much foreign matter is contained in lubricating oil, so that the remaining foreign matter may enter the operation mechanisms.
It is an object of the present invention to reliably prevent foreign matter such as wear dust (iron dust, etc.) occurring in a rolling bearing from flowing out of the bearing space of the rolling bearing, in particular, from entering an operation mechanism located midway of a circulation path through which lubricating oil circulates.